Streakline visualization apparatus and method

1. A streakline visualization apparatus for calculating a streakline indicating a series of particles at a plurality of analysis time points in fluid simulation time and displays the streakline, the streakline visualization apparatus comprising: a memory configured to store structure information indicating temporal change of a shape of a structure in an analysis space and fluid information indicating at least one of spatial change and temporal change of a velocity of fluid at a plurality of points in a region where the fluid exists in the analysis space; and a processor coupled to the memory and configured to perform a procedure including: setting, when calculating a second streakline at a second analysis time point based on a first streakline at a first analysis time point, a partial region including a discrete point at a first position on the first streakline in the analysis space as an analysis target region of the discrete point, calculating, based on the velocity of the fluid in the analysis target region, the velocity indicated by the fluid information, a second position indicating a destination of a particle on the discrete point at the second analysis time point, determining, based on information about the structure in the analysis target region, the information indicated by the structure information, a region occupied by the structure in the analysis target region at the second analysis time point, determining entrance or non-entrance of the second streakline into the occupied region based on the first position and the second position, setting, when determining that the second streakline has entered the occupied region, at least a third analysis time in a time period between the first analysis time point and the second analysis time point, calculating a third position indicating a destination of the particle on the discrete point at a third analysis time point, and recalculating the second position based on the third position.

2. The streakline visualization apparatus according to claim 1 , wherein the setting of the analysis target region includes calculating a maximum velocity of the fluid in a time period between the first analysis time point and the second analysis time point and calculating a radius of the analysis target region as a spherical region based on a difference between the first analysis time point and the second analysis time point and the maximum velocity.

3. The streakline visualization apparatus according to claim 2 , wherein the setting of the analysis target region includes setting a minimum value as the radius of the analysis target region based on an interval between a plurality of points in the region where the fluid exists and setting, when the calculated radius is smaller than the minimum value, the minimum value as the radius of the analysis target region.

4. The streakline visualization apparatus according to claim 3 , wherein the setting of the analysis target region includes, in a case that calculation of the second position with the set radius is not completed, recalculating the second position with a maximum radius value as the radius of the analysis target region, calculating a radius that minimizes a calculation amount including a calculation amount for the recalculation of the second position, and setting, when the calculated radius is smaller than the minimum value, the minimum value as the radius of the analysis target region.

5. The streakline visualization apparatus according to claim 2 , wherein the setting of the analysis target region includes the radius of the analysis target region that is smaller than a value calculated by multiplying the difference between the first analysis time point and the second analysis time point by the maximum velocity, and wherein the calculating of the second position includes, when the destination of the particle on the discrete point has fallen outside the analysis target region, recalculating the second position by expanding the analysis target region.

6. The streakline visualization apparatus according to claim 1 , wherein the determining of the entrance or non-entrance includes performing a first determination of whether the second position has fallen inside the fluid, performing a second determination of whether a line connecting the first position and the second position has crossed a surface of the structure, and determining whether the second streakline has entered the occupied region based on results of the first determination and the second determination.

7. The streakline visualization apparatus according to claim 1 , wherein the procedure further includes, displaying, when determining that the second streakline has not entered the occupied region, the second streakline passing through the second position.

8. A streakline visualization method for calculating a streakline indicating a series of particles at a plurality of analysis time points in fluid simulation time and displaying the streakline, the streakline visualization method comprising: setting, by a processor, when calculating a second streakline at a second analysis time point based on a first streakline at a first analysis time point, a partial region including a discrete point at a first position on the first streakline in an analysis space as an analysis target region of the discrete point; referring to, by the processor, fluid information indicating at least one of spatial change and temporal change of a velocity of fluid at a plurality of points in a region where the fluid exists in the analysis space and calculating, based on the velocity of the fluid in the analysis target region, a second position indicating a destination of a particle on the discrete point at the second analysis time point; referring to, by the processor, structure information indicating temporal change of a shape of a structure in the analysis space and determining, based on information about the structure in the analysis target region, a region occupied by the structure in the analysis target region at the second analysis time point; determining, by the processor, entrance or non-entrance of the second streakline into the occupied region based on the first position and the second position; setting, when determining that the second streakline has entered the occupied region, at least one third analysis time in a time period between the first analysis time point and the second analysis time point; calculating a third position indicating a destination of the particle on the discrete point at the third analysis time point; and recalculating the second position based on the third position.

9. A non-transitory computer-readable storage medium storing a computer program that causes a computer to perform a procedure including calculating a streakline indicating a series of particles at a plurality of analysis time points in fluid simulation time and displaying the streakline, the procedure comprising: setting, when calculating a second streakline at a second analysis time point based on a first streakline at a first analysis time point, a partial region including a discrete point at a first position on the first streakline in an analysis space as an analysis target region of the discrete point; referring to fluid information indicating at least one of spatial change and temporal change of a velocity of fluid at a plurality of points in a region where the fluid exists in the analysis space and calculating, based on the velocity of the fluid in the analysis target region, a second position indicating a destination of a particle on the discrete point at the second analysis time point; referring to structure information indicating temporal change of a shape of a structure in the analysis space and determining, based on information about the structure in the analysis target region, a region occupied by the structure in the analysis target region at the second analysis time point; determining entrance or non-entrance of the second streakline into the occupied region based on the first position and the second position; setting, when determining that the second streakline has entered the occupied region, at least one third analysis time in a time period between the first analysis time point and the second analysis time point; calculating a third position indicating a destination of the particle on the discrete point at the third analysis time point; and recalculating the second position based on the third position.